A backflow valve, also known as a backwater valve, is used to prevent a reversal of flow in a flow line. An example of a backflow valve is disclosed in Canadian Patent 2,114,602 and corresponding U.S. Pat. No. 5,406,972 granted to Coscarella et al.
The Coscarella et al reference discloses a backflow valve that has a pivoting closure gate with an open position to accommodate flow in a desired flow direction and a closed position to close off the flow line when there is a reversal of flow. The closure gate is hinged to the bottom of the valve housing. In the open position, flow passes over the closure gate with the closure gate serving as a spillway. Secured to the closure gate is a float. When the level of liquid rises, the float causes the closure gate to rise and the reversed direction of flow pushes the closure gate into the closed position.
The disadvantage of the backflow valve disclosed in the Coscarella et al reference is that when in the open position the liquid flow is always passing over the closure gate. In some applications, it would be advantageous to have a side mounted closure gate with the closure gate positioned to one side of the flow stream in order to reduce the exposure of the closure gate to the liquid flow. The closure gate disclosed in Coscarella et al, however, would not operate if the valve body of Coscarella et al were positioned on its side.